The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A cam phaser control system may include a cam phaser actuator imposed between an engine camshaft and a camshaft drive such that an engine valve timing may be varied. Some systems use engine oil as a hydraulic fluid to move the phaser actuator. Typically, the oil flowing into or out of the actuator is controlled by a multi-port, electrically-controlled oil control valve (OCV). The position of the OCV (and, thus, the flow of oil into or out of a specific port of the actuator) is controlled via a Pulse Width Modulated (PWM) voltage source. A closed-loop controller imparts an appropriate PWM value to move the phaser actuator to a desired phaser position.
Due to degradation of either the cam phaser actuator, the OCV, or the oil supply source, the observed closed-loop control may significantly deviate from expected closed-loop control. For example, a rate of change of a measured phaser position may vary from a commanded change in desired phaser position. This variance may indicate that the phaser actuator is either moving slower than expected or moving faster than expected, depending on the specific type of degradation. These deviations may cause the vehicle driver to experience undesirable vehicle surge at varying levels.